Refactor deploy_key_multiple_projects API documentation [ci skip]

doc/api/deploy_key_multiple_projects.md

 # Adding deploy keys to multiple projects
-If you want to easily add the same deploy key to multiple projects in the same group, this can be achieved quite easily with the API.
-First, find the ID of the projects you're interested in, by either listing all projects:
+If you want to easily add the same deploy key to multiple projects in the same
+group, this can be achieved quite easily with the API.
+First, find the ID of the projects you're interested in, by either listing all
+projects:
 ```
-curl --header 'PRIVATE-TOKEN: abcdef' https://gitlab.com/api/v3/projects
+curl -H 'PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK' https://gitlab.example.com/api/v3/projects
 ```
-Or finding the id of a group and then listing all projects in that group:
+Or finding the ID of a group and then listing all projects in that group:
 ```
-curl --header 'PRIVATE-TOKEN: abcdef' https://gitlab.com/api/v3/groups
+curl -H 'PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK' https://gitlab.example.com/api/v3/groups
 # For group 1234:
-curl --header 'PRIVATE-TOKEN: abcdef' https://gitlab.com/api/v3/groups/1234
+curl -H 'PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK' https://gitlab.example.com/api/v3/groups/1234
 ```
 With those IDs, add the same deploy key to all:
+
 ```
 for project_id in 321 456 987; do
-    curl -X POST --data '{"title": "my key", "key": "ssh-rsa AAAA..."}' --header 'PRIVATE-TOKEN: abcdef' https://gitlab.com/api/v3/projects/${project_id}/keys
+    curl -X POST -H "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" -H "Content-Type: application/json" \
+    --data '{"title": "my key", "key": "ssh-rsa AAAA..."}' https://gitlab.example.com/api/v3/projects/${project_id}/keys
 done
 ```